Newsfood.com reports that certain proteins in birch pollen and soy beans are so similar that people who are allergic to birch pollen may experience an allergic reaction after eating soy; this is known as cross allergy or oral allergy syndrome.

Those with a birch pollen allergy may also experience cross reactions with peanuts, hazelnuts, apples, celery, strawberries, and carrots. Typical symptoms include itching of the mouth, hay fever, skin rashes, and digestive problems.